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*RNP (BaroVNAV) glidepath is not at straight-line path as in ILS or LPV. It is curved
because it is based on barometric altimetry, which follows the curvature of the earth.
1.4.7 Final Approach Segment (FAS).
The FAS begins at the PFAF and ends at the landing threshold point (LTP). The
FAS is typically aligned with the runway centerline extended. The segment OEA
is divided into the FAS OCS and the visual segment obstacle identification
surface (OIS).
1.4.8 Flight Path Control Point (FPCP).
The FPCP is a 3-D point defined by the LTP geographic position, mean sea level
(MSL) elevation, and threshold crossing height (TCH) value. The FPCP is in the
vertical plane of the final approach course and is used to relate the glidepath
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angle of the final approach track to the landing runway. It is sometimes referred
to as the TCH point or reference datum point (RDP). See figure 1-1.
1.4.9 Final Roll-Out Point (FROP).
Where a course change is required within the FAS, the point that the aircraft rolls
to a wings-level attitude aligned with the runway centerline extended is
considered the FROP (see figure 1-4).
Figure 1-4. FROP
Roll-out Point
LTP
1.4.10 Geographic Positioning Navigation (GPN).
Navigation based on geodetic calculation of geographic position referenced to
the WGS-84 ellipsoid. Global positioning system (GPS), wide area augmentation
system (WAAS), local area augmentation system (LAAS), flight management
system (FMS), RNP, and area navigation (RNAV) are examples of GPN.
1.4.11 Glidepath Angle (GPA).
The GPA is the angle of the final approach descent path relative to the ASBL. In
this document, GPA is represented in calculations as the Greek symbol theta (θ).
See figure 1-1.
1.4.12 Ground Point of Intercept (GPI).
The glidepath intercepts the ASBL at the GPI. The GPI is expressed as a
distance in feet from the LTP. The GPI is derived from TCH and glidepath angle
values: tan( )
GPI TCH
θ
= . See figure 1-1.
1.4.13 Height Above Touchdown (HAT).
The HAT is the height of the DA above the highest point in the first 3,000 ft of the
landing runway (touchdown zone elevation). See figure 1-5.
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Figure 1-5. HAT
DA
LTP
Runway ASBL
Glidepath
HAT
3,000’
1.4.14 Landing Threshold Point (LTP).
The LTP is the point where the runway centerline (RCL) intersects the runway
threshold (RWT). WGS-84/NAD-83 geographic coordinates and height above
mean sea level define the LTP (see figures 1-1 and 1-5).
1.4.15 Obstacle Clearance Surface (OCS).
The OCS is an inclined surface conforming to the lateral dimensions of the
obstacle evaluation area. An OCS is normally associated with evaluation of 3-D
final segments or missed approach/departure climb segments.
1.4.16 Obstacle Evaluation Area (OEA).
The OEA is an area within which obstructions are evaluated by application of the
ROC, OCS, or OIS to achieve appropriate vertical clearance. The OEA conforms
to the lateral RNP segment width limits.
1.4.17 Obstacle Identification Surface (OIS).
The OIS is an inclined surface conforming to the lateral dimensions of the OEA
used for identification of obstacles that may require mitigation to maintain the
required level of safety for the applicable segment. An OIS is normally
associated with the visual portion of the FAS.
1.4.18 Radius to Fix (RF) Leg.
An RF leg is a constant radius circular path about a defined turn center that
terminates at a fix.
1.4.19 Required Navigation Performance (RNP).
RNP is a statement of the navigational performance required to maintain flight
within the OEA associated with instrument procedure segments.
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1.4.20 Required Obstruction Clearance (ROC).
Sometimes referred to as required obstacle clearance, ROC is the minimum
vertical clearance (in feet) that must exist between aircraft and the highest
ground obstruction within the OEA of instrument procedure segments.
1.4.21 Runway Threshold (RWT).
The RWT marks the beginning of the portion of the runway usable for landing. It
extends the full width of the runway (see figure 1-6).
Figure 1-6. LTP/RWT
RWT
RCL
LTP
1.4.22 Special Aircraft and Aircrew Authorization Required (SAAAR).
Aircraft may be equipped beyond the minimum standard for public RNP criteria
and aircrews trained to achieve a higher level of instrument approach
performance. SAAAR criteria are based on a higher level of equipage and
additional aircrew requirements. Procedures that utilize SAAAR design criteria
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